The simplest event possible, consists of a title, speaker, dates, description, plus attached files. It does not contain a timetable.
Create a meeting if you wish to handle a timetable with several items inside, attach files to them
You should choose to create a conference only if you need advanced features such as call for abstract, registration form, accomodation form, etc. The Conference type creates a real web portal to your event, not just a timetable.